Among petroleum products, for example, lubricant, gas oil, and jet fuel are products in which importance is placed on cold flow property. Consequently, it is desirable that the base oil used for these products is such that its wax component, such as a normal paraffin or a slightly branched isoparaffin, which is a factor in deterioration of cold flow property, has been completely or partially removed, or converted into a component other than a wax component.
An example of a known dewaxing technique for removing the wax component from a hydrocarbon oil is a method in which the wax component is extracted using a solvent such as liquefied propane or MEK. However, this method suffers from the problem which is, for example that operating costs are high, the types of feedstock that can be used are limited, and the product yield is limited by the type of feedstock.
On the other hand, an example of a known dewaxing technique for converting the wax component in a hydrocarbon oil into a non-wax component is isomerization and dewaxing, in which the hydrocarbon oil is brought into contact with, in the presence of hydrogen, a bifunctional hydroisomerization catalyst capable of hydrogenation-dehydrogenation and isomerization, thereby isomerizing normal paraffins in the hydrocarbon oil to isoparaffins (e.g., Patent Literature 1).